Is it normal to have too many idle processes in postgresql cluster?

[Abdul Qoyyuum <aqoyyuum@xxxxxxxxxxxxxxxxx>]

Hi all, I have a database cluster running Postgresql 9.6 on RHEL 6 servers. I've noticed a lot of idle processes in the master database as opposed to the slave database and from the looks of pg_activity, they're all idle statements like "SELECT 1". Forums and StackOverflow seems to suggest its nothing to worry about but 

[user@xxxxxx ~]$ ps -ef | grep postgres | grep idle | wc -l
213  

Seems to get me worried. Should I be worried? Is this normal? If not, what should I do?
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Abdul Qoyyuum Bin Haji Abdul Kadir

HP No: +673 720 8043